{
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\begin{tabular}{l*{6}{c}}
\hline\hline
            &\multicolumn{1}{c}{(1)}&\multicolumn{1}{c}{(2)}&\multicolumn{1}{c}{(3)}&\multicolumn{1}{c}{(4)}&\multicolumn{1}{c}{(5)}&\multicolumn{1}{c}{(6)}\\
            &\multicolumn{1}{c}{dpopdens50}&\multicolumn{1}{c}{dpopdens50}&\multicolumn{1}{c}{dpopdens50}&\multicolumn{1}{c}{dpopdens50}&\multicolumn{1}{c}{dpopdens50}&\multicolumn{1}{c}{dpopdens50}\\
\hline
dpopdens45  &     -0.7120\sym{a}&     -0.7695\sym{a}&     -0.8251\sym{a}&     -0.8769\sym{a}&     -0.8525\sym{a}&     -0.9371\sym{a}\\
            &    (0.0271)       &    (0.0390)       &    (0.0476)       &    (0.0581)       &    (0.0525)       &    (0.0451)       \\
\hline
\(N\)       &         174       &         174       &         174       &         174       &         174       &         158       \\
\(R^{2}\)   &       0.808       &       0.837       &       0.831       &       0.859       &       0.874       &       0.874       \\
\hline\hline
\multicolumn{7}{l}{\footnotesize Standard errors in parentheses}\\
\multicolumn{7}{l}{\footnotesize \sym{c} \(p<0.1\), \sym{b} \(p<0.05\), \sym{a} \(p<0.01\)}\\
\end{tabular}
}
